I will just add that this feature is available in nixos http://nixos.org/wiki/Nix%28OS%29_related_repositories_and_work 2013/8/30 Cyprien Nicolas > Il y a 20 heures, Ludovic Courtès écrivit : > > > Amirouche Boubekki skribis: > > > > > What about the possiblity to use overlays ? > > > > Could you elaborate? > > > > I hear this comes from the Gentoo jargon, but I’m not sure what > > that means. > > I like the idea. I'll try to elaborate myself, as a Gentoo user for > years ;-) I describe them from my own experience, official > documentation can be found there [1] > > In Gentoo, ebuilds (the files that specify how to build a package from > source) are stored in the "portage tree", which is the official > repository. The tree consists of directories, one per category, plus > one sub-directory par package, where package directories contains one > or more ebuilds, one ebuild per package version. (plus some > additional files, like patches.) > > "Portage" (the tool used to install packages from source, through the > "emerge" command) looks for ebuild in that directory, but it can also > looks from other directories which follow the same structure, those > directories are called "overlays", as they can mask packages from the > official tree, but also extend it. > > They are plenty of overlays usage: experimental packages, > user-contributed packages, locally used packages for testing purposes… > > > However, overlay create new concerns. First, priority of overlays, if > two provide the same package-version combination, which one to choose? > If Overlay A provide Package P, which depends on Library L, not in > Overlay A but in the "base" repository, and that Overlay B provide > a newer version of Library L, which L to choose? > > Handling build failure of packages using overlays can be quite tricky > too. ;-) > > And last, how and where to "centralize" overlays, in order to give > user a tool to easily add, remove, update overlays. > > > 1. http://www.gentoo.org/proj/en/overlays/userguide.xml > > -- > Cyprien/Fulax >